Product Report: MaxxForce carries on DT lineage

Of the seven models of MaxxForce engines International is introducing (see January’s Engine Notebook), the one most contractors will find under the hood is the MaxxForce DT. This inline six-cylinder is the successor to International’s venerable DT 466. The MaxxForce DT retains the earlier DT’s wet-sleeve design and 7.6-liter displacement and is available with 210 to 300 horsepower and 520 to 860 foot-pounds of torque. Intended applications are Class 6 and 7 trucks (19,501 to 33,000 pounds GVW), which includes a broad range of vocational configurations.

The MaxxForce DT has a number of major changes from its predecessor, most of them driven by the 2007 emissions regulations. Although International has been meeting ’07 emissions standards since 1999 with their Green Diesel Technology, further refinements have been made for these production engines.

The electronic engine control module now sports a 32-bit processor and expanded feature set to handle the demands of aftertreatment systems. This single ECM replaces a two-box setup International had been using and reduces the number of connections by half. A second EGR cooler provides additional cooling of recirculated exhaust gases before they re-enter the cylinder, further reducing NOx (oxides of nitrogen) emissions.

At the heart of the new closed crankcase ventilation system is a maintenance-free centrifugal separator; no replacement filter is required. During combustion, some gases get past the piston rings (“blow-by”) and are trapped in the crankcase. In the past, these gases were vented to the outside, but that’s bad for the environment. Engines are now closed systems; gases are kept inside and are run back through the engine. The oil contained in these crankcase fumes has to be removed before it reaches the engine. Some systems use paper or foam filters that have to be replaced or cleaned. International’s centrifugal system spins the fumes and the heavier oil is flung to the outside. Only clean gases make it back into the engine while the recaptured oil is fed back to the crankcase.

Diesel particulate filters are common on ’07 emissions engines, and like other DPFs, the DT’s unit requires an occasional burst of raw fuel in order to burn off the particulate matter that accumulates on the filter’s substrate. Rather than add extra hardware to supply this fuel, International relies on the engine’s second generation (G2) injectors to perform the task. An extra injection event delivers fuel to the cylinder after the combustion cycle. This fuel is carried out the exhaust valves into the exhaust system for active regeneration of the DPF. Regeneration occurs only as often and as long as is necessary to maintain efficient operation of the filter.

It’s a clever, simple design. “Our goal was to enable consistent regeneration with a minimum of additional cost and complexity,” says Phil Gronberg, chief engineer for the Inline Medium-Duty Engines at International.

Among the many chassis available with the MaxxForce DT engine, those best suited for vocational applications will be the DuraStar (medium duty) and WorkStar (severe duty) platforms. While the engines are considered 2007 models, the trucks will be ’08s even though they will be phased in starting this year.

Standard transmissions are available, but International is expanding their offering of Allison and Eaton automatic and automated manual transmissions. “We know that automatics and automated manuals improve productivity,” says Jack Allen, president of International’s engine group. “This has been demonstrated in our experience with beverage and (pickup and delivery) fleets. But we also know that in many markets contractors and building materials suppliers struggle to find qualified workers. By offering these transmissions, we’re removing one more hurdle applicants have to get over on their way to filling a position.”